A considerable number of recent papers have appeared on the subject of two-sector growth models, examining many of the questions of interest in the fields of capital theory and growth however, the emphasis has been on deriving general propositions about growth rates and stability, the influence of technical progress, relative price changes, and savings behavior. Almost no attempt has been made to fit these models to actual data. In this paper a means of overcoming this difficulty is suggested. The approach is to use completely aggregated data for the inputs, allocating the total factor supplies between sectors so that marginal efficiency conditions are satisfied. The only sectoral data required are ratios of gross investment to GNP and ratios of consumer goods prices to capital goods prices. Estimates of the historical course of technical progress in the consumer and capital goods sectors of the United States during the period 1929-1955 are also provided. The estimates are based on a simple two-sector model in which technical advances are shared by all existing machines.